U.S. patent application number 12/041532 was filed with the patent office on 2009-09-03 for method for inspecting magnetic characteristics of a plurality of thin magnetic heads by means of local application of magnetic field.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Koji SHIMAZAWA.
Application Number | 20090219018 12/041532 |
Document ID | / |
Family ID | 41012694 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090219018 |
Kind Code |
A1 |
SHIMAZAWA; Koji |
September 3, 2009 |
METHOD FOR INSPECTING MAGNETIC CHARACTERISTICS OF A PLURALITY OF
THIN MAGNETIC HEADS BY MEANS OF LOCAL APPLICATION OF MAGNETIC
FIELD
Abstract
A method for inspecting magnetic characteristics of a thin film
magnetic head that is arranged in a row bar includes: a step of
preparing a row bar having sliders including a thin film magnetic
head formed therein and lapping guides having magnetoresistance
effect; a step of preparing a magnetic field applying row bar
having first and second magnetic field applying elements; a first
positioning step in which said magnetic field applying row bar is
arranged opposite to said row bar; a second positioning step in
which a relative movement between said magnetic field applying row
bar and said row bar is made so that at least one of said lapping
guides exhibits a largest output voltage; and a measurement step in
which a relationship between the intensity of the magnetic field
and an output voltage of a magnetic field sensor is obtained.
Inventors: |
SHIMAZAWA; Koji; (Tokyo,
JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
TDK CORPORATION
Tokyo
JP
|
Family ID: |
41012694 |
Appl. No.: |
12/041532 |
Filed: |
March 3, 2008 |
Current U.S.
Class: |
324/210 |
Current CPC
Class: |
G01R 33/1207
20130101 |
Class at
Publication: |
324/210 |
International
Class: |
G01R 33/12 20060101
G01R033/12 |
Claims
1. A method for inspecting magnetic characteristics of a thin film
magnetic head that is arranged in a row bar, comprising: a step of
preparing a row bar having a plurality of sliders which are
arranged along a longitudinal direction of said row bar, each
slider including a thin film magnetic head formed therein, wherein
said row bar is provided with lapping guides having
magnetoresistance effect, said lapping guides being located at
least two positions which are selected from positions between the
sliders adjacent to each other and positions at both ends of said
row bar; a step of preparing a magnetic field applying row bar
having first magnetic field applying elements, each of which
corresponds to each thin film magnetic head, and having at least
two second magnetic field applying elements, each of which
corresponds to each of the at least two lapping guides; a first
positioning step in which said magnetic field applying row bar is
arranged opposite to said row bar such that a magnetic pole end of
each first magnetic field applying element faces a magnetic field
sensor of the corresponding thin film magnetic head and such that a
magnetic pole end of each second magnetic field applying element
faces the corresponding lapping guide; a second positioning step in
which a magnetic field is applied from said second magnetic field
applying elements to said lapping guides while an electric current
is applied to said lapping guide, and in which a relative movement
between said magnetic field applying row bar and said row bar is
made so that at least one of said lapping guides exhibits a largest
output voltage, said second positioning step being carried out
after said first positioning step; and a measurement step in which
an alternating magnetic field is applied, from said first magnetic
field applying element to said magnetic field sensor of said thin
film magnetic head, while an electric current is applied to said
magnetic field sensor, and while intensity of the magnetic field is
changed, and in which a relationship between the intensity of the
magnetic field and an output voltage of the magnetic field sensor
is obtained, said measurement step being carried out after said
second positioning step.
2. The method according to claim 1, further comprising a third
positioning step in which a magnetic field is applied from said
first magnetic field applying element to said magnetic field sensor
of said thin film magnetic head, while an electric current is
applied to said magnetic field sensor, and in which a relative
movement between said magnetic field applying row bar and said row
bar is made so that said magnetic field sensor exhibits a largest
output voltage, said third positioning step being carried out after
said second positioning step and prior to said measurement
step.
3. The method according to claim 1, wherein the relative movement
of said magnetic field applying row bar and said row bar is made in
a form of a rectilinear movement in direction "x", in a form of a
rectilinear movement in direction "y", or in a form of a rotational
movement about direction "z", or in a form of a combination
thereof, wherein said direction "x" is defined to be the
longitudinal direction of said row bar, said direction "y" is
defined to be a direction that is perpendicular to a film plane of
said magnetic field applying row bar, and said direction "z" is
defined to be a direction that is perpendicular both to the
direction "x" and to the direction "y".
4. The method according to claim 1, wherein said thin film magnetic
head is provided with a pair of magnetic layers whose magnetization
directions change according to an external magnetic field, the pair
of magnetic layers serving as said magnetic field sensor, wherein
said thin film magnetic head is further provided with a pair of
shield layers which sandwich said pair of magnetic layers in a
stacking direction thereof, said pair of shield layers being
magnetized in track width directions that are anti-parallel to each
other, and wherein each of said pair of magnetic layers is
exchange-coupled with the shield layer that is adjacent
thereto.
5. A method for manufacturing a thin film magnetic head, including
the method according to claim 1.
6. A magnetic field applying row bar that is used to inspect
magnetic characteristics of a thin film magnetic head that is
arranged in a row bar, wherein said row bar has a plurality of
sliders which are arranged along a longitudinal direction of said
row bar, each slider including a thin film magnetic head formed
therein, wherein said row bar is provided with lapping guides
having magnetoresistance effect, said lapping guides being located
at at least two positions which are selected from positions between
the sliders adjacent to each other and positions at both ends of
said row bar, comprising: a plurality of first magnetic field
applying elements that are located such that a magnetic pole end of
each first magnetic field applying element faces a magnetic field
sensor of said thin film magnetic head when said magnetic field
applying row bar is arranged opposite to said row bar; and at least
two second magnetic field applying elements that are located such
that magnetic pole ends thereof face at least two of said lapping
guides when said magnetic field applying row bar is arranged
opposite to said row bar; wherein said first magnetic field
applying element is capable of applying an alternating magnetic
field to said magnetic field sensor that is opposite thereto while
varying intensity of the magnetic field, and said second magnetic
field applying element is capable of applying a magnetic field to
said lapping guide that is opposite thereto.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for inspecting
magnetic characteristics of thin film magnetic heads, more
particularly, to a method for inspecting thin film magnetic heads
arranged in a row bar.
[0003] 2. Description of the Related Art
[0004] Conventionally, thin film magnetic heads are manufactured by
the following steps. First, a stack that includes a magnetic field
sensor (a read head portion) and a write head portion is formed on
a substrate in the wafer process. Next, the wafer is diced and
separated into row bars. A plurality of sliders is disposed in each
row bar along the longitudinal direction thereof, and each slider
is provided with a thin film magnetic head that is formed in the
wafer process. A row bar serves as a work unit in a lapping step
for forming an air bearing surface. When lapping is completed, the
row bar is separated into individual sliders, each of which is then
assembled into a head gimbal assembly and mounted on a hard disk
drive in the final process.
[0005] The thin film magnetic head, prior to being finished as a
slider and being sent to a subsequent process, undergoes an
inspection of magnetic characteristics and other tests.
Conventionally, sliders are separately attached to a dedicated
inspection apparatus, called the spin stand, and inspected one by
one. This method enables sliders to be inspected in the same
environment as in a state in which the sliders are actually mounted
on hard disk drives, but is disadvantageous as regards the
efficiency of the inspection. Accordingly, there has been proposed
a method for collectively inspecting sliders that are
mass-produced.
[0006] Japanese Patent Laid-Open Publication No. 150264/94
discloses an inspection method called quasi-static test (QST). The
test, which is performed prior to the final assembling of hard disk
drives, simulates an actual environment. Specifically, an
alternating magnetic field (refers to an alternately changing
magnetic field) that is generated by a magnetic field generator is
applied from the outside, instead of a magnetic field emitted from
a recording medium, in order to collectively measure and evaluate
various magnetic characteristics of a plurality of sliders arranged
in a row bar. A Helmholtz coil is used as the magnetic field
generator. Application of high-frequency alternating current to the
Helmholtz coil causes the Helmholtz coil to generate an alternating
magnetic field. The row bar is placed in front of the Helmholtz
coil so that an alternating magnetic field is applied to magnetic
field sensors. The alternating magnetic field simulates a varying
magnetic field, which corresponds to signal "0" and "1", that the
magnetic field sensors receive from a rotating magnetic disk in an
actual environment. A sense current is generated to flow in the
magnetic field sensors by means of probes. In accordance with a
change in the magnetic field, the output voltage of the magnetic
field sensor changes due to magnetoresistance effect. In this way,
the relationship between the external magnetic field and the signal
output (output voltage) can be obtained. The data that are obtained
are used to evaluate the magnetic characteristics of the magnetic
field sensors and to prevent defective sliders from being sent to a
subsequent process.
[0007] In recent years, ultra-high recording density of hard disk
drives has been promoted. The ultra-high recording density
essentially requires ultra-high linear recording density. The
ultra-high linear recording density means an increase in the
frequency of an alternating magnetic field that is applied to a
thin film magnetic head. Accordingly, it is preferable that thin
film magnetic heads that realize the ultra-high linear recording
density be inspected under the environment of an alternating
magnetic field having an ultra-high frequency. However, in a
conventional Helmholtz coil, there is a limitation to an increase
in the frequency of an alternating magnetic field because of the
characteristics of the device. Frequencies in the order of several
hundred kilohertz are within the capability of the Helmholtz coil,
but frequencies higher than 1 megahertz are difficult to achieve.
However, alternating magnetic fields in the order of several
megahertz are found in the actual environment of hard disk drives.
Thus, it has already been difficult to completely simulate the
actual environment by a conventional QST. Use of a spin stand may
realize such high frequencies, but will lead to inefficiency in the
inspection.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a method
for inspecting magnetic characteristics of thin film magnetic heads
in an efficient manner, the method being capable of sufficiently
simulating a high-frequency alternating magnetic field. Another
object of the present invention is to provide a magnetic field
applying bar which can be suitably used in the method for
inspecting the magnetic characteristics of thin film magnetic
heads.
[0009] According to an embodiment of the present invention, a
method for inspecting magnetic characteristics of a thin film
magnetic head that is arranged in a row bar comprises: a step of
preparing a row bar having a plurality of sliders which are
arranged along a longitudinal direction of said row bar, each
slider including a thin film magnetic head formed therein, wherein
said row bar is provided with lapping guides having
magnetoresistance effect, said lapping guides being located at
least two positions which are selected from positions between the
sliders adjacent to each other and positions at both ends of said
row bar; a step of preparing a magnetic field applying row bar
having first magnetic field applying elements, each of which
corresponds to each thin film magnetic head, and having at least
two second magnetic field applying elements, each of which
corresponds to each of the at least two lapping guides; a first
positioning step in which said magnetic field applying row bar is
arranged opposite to said row bar such that a magnetic pole end of
each first magnetic field applying element faces a magnetic field
sensor of the corresponding thin film magnetic head and such that a
magnetic pole end of each second magnetic field applying element
faces the corresponding lapping guide; a second positioning step in
which a magnetic field is applied from said second magnetic field
applying elements to said lapping guides while an electric current
is applied to said lapping guide, and in which a relative movement
between said magnetic field applying row bar and said row bar is
made so that at least one of said lapping guides exhibits a largest
output voltage, said second positioning step being carried out
after said first positioning step; and a measurement step in which
an alternating magnetic field is applied, from said first magnetic
field applying element to said magnetic field sensor of said thin
film magnetic head, while an electric current is applied to said
magnetic field sensor, and while intensity of the magnetic field is
changed, and in which a relationship between the intensity of the
magnetic field and an output voltage of the magnetic field sensor
is obtained, said measurement step being carried out after said
second positioning step.
[0010] According to the inspection method described above, the
magnetic pole end of each first magnetic field applying element is
disposed opposite to the magnetic field sensor of the thin film
magnetic head, and a magnetic field is individually applied to the
magnetic field sensor of the thin film magnetic head from the
corresponding first magnetic field applying element. In other
words, each first magnetic field applying element only needs to
apply a predetermined magnetic field to the magnetic field sensor
of the corresponding thin film magnetic head. In addition, the
required intensity of the generated magnetic field can be
sufficiently small because the magnetic field applying bar is
arranged opposite to a row bar. This facilitates generation of a
significantly high frequency alternating magnetic field and makes
it possible to more precisely simulate an alternating magnetic
field that is generated in an actual environment in hard disk
drives, as compared with a case in which a large-sized conventional
Helmholtz coil is used.
[0011] Further, this inspection method includes two kinds of
positioning steps. The first positioning step is a positioning step
for arranging the magnetic field applying bar opposite to the row
bar with, so to speak, mechanically achievable accuracy. The first
positioning step enables a rough adjustment of the positional
relationship between the first magnetic field applying element and
the magnetic field sensor of the corresponding thin film magnetic
head. The second positioning step, which makes use of a lapping
guide, provides a more precise positioning step that utilizes
magnetic properties. The lapping guide used herein refers to an
element that is particularly provided in order to form the element
height of a magnetic field sensor into a predetermined range in the
lapping process. The lapping guide, whose element height decreases
as lapping progresses and whose electrical resistance increases, is
used in order to control the lapping amount while monitoring the
electrical resistance thereof by using the above characteristics.
In the present embodiment, the lapping guide is formed of a
material having the magnetoresistance effect. Hence, when a
magnetic field is applied from the second magnetic field applying
element to the lapping guide and a relative movement is made
between the magnetic field applying bar and the row bar, the
intensity of the magnetic field that the lapping guide receives
changes due to the magnetoresistance effect, and thereby a
variation in the output voltage of the lapping guide is caused. By
adjusting the relative positional relationship between the magnetic
field applying bar and the row bar such that the output voltage is
maximized, the lapping guide comes to a position that is
substantially opposite to the second magnetic field applying
element. As a result, the first magnetic field applying elements
also come to positions that are substantially opposite to the
magnetic field sensors of the thin film magnetic heads.
[0012] The reason that importance is placed on the positioning of
the first magnetic field applying element and the magnetic field
sensor of the thin film magnetic head, as described above, is
because the magnetic field sensor has a significantly small
dimension in the track width direction thereof. Thin film magnetic
heads today have a width in the order of several tens of nanometers
in the track width direction, and therefore, common mechanical
methods are hardly applicable for the positioning of the first
magnetic field applying element and the magnetic field sensor of
the thin film magnetic head. This is a problem that does not occur
when a Helmholtz coil is used to collectively apply a magnetic
field. However, the inspection method of the present embodiment is
capable of meeting such a requirement without difficulty.
[0013] According to another embodiment of the present invention,
the method for inspecting magnetic characteristics of a thin film
magnetic head that is arranged in a row bar further comprises a
third positioning step in which a magnetic field is applied from
said first magnetic field applying element to said magnetic field
sensor of said thin film magnetic head, while an electric current
is applied to said magnetic field sensor, and in which a relative
movement between said magnetic field applying row bar and said row
bar is made so that said magnetic field sensor exhibits a largest
output voltage, said third positioning step being carried out after
said second positioning step and prior to said measurement step. In
general, a magnetic field sensor has a significantly smaller
dimension than a lapping guide. Accordingly, by using the magnetic
field sensor and the first magnetic field applying element in order
to perform a process similar to the second positioning step, the
first magnetic field applying elements can be positioned more
precisely at positions that are substantially opposite to the
magnetic field sensors of the thin film magnetic heads.
[0014] According to yet another embodiment of the present
invention, a magnetic field applying row bar is used to inspect
magnetic characteristics of a thin film magnetic head that is
arranged in a row bar, wherein said row bar has a plurality of
sliders which are arranged along a longitudinal direction of said
row bar, each slider including a thin film magnetic head formed
therein, wherein said row bar is provided with lapping guides
having magnetoresistance effect, said lapping guides being located
at least two positions which are selected from positions between
the sliders adjacent to each other and positions at both ends of
said row bar. The magnetic field applying row bar comprises: a
plurality of first magnetic field applying elements that are
located such that a magnetic pole end of each first magnetic field
applying element faces a magnetic field sensor of said thin film
magnetic head when said magnetic field applying row bar is arranged
opposite to said row bar; and at least two second magnetic field
applying elements that are located such that magnetic pole ends
thereof face at least two of said lapping guides when said magnetic
field applying row bar is arranged opposite to said row bar. The
first magnetic field applying element is capable of applying an
alternating magnetic field to said magnetic field sensor that is
opposite thereto while varying intensity of the magnetic field, and
said second magnetic field applying element is capable of applying
a magnetic field to said lapping guide that is opposite
thereto.
[0015] The above and other objects, features and advantages of the
present invention will become apparent from the following
description with reference to the accompanying drawings which
illustrate examples of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a conceptual cross-sectional view of a thin film
magnetic head that is applicable to a method for inspecting the
magnetic characteristics of the thin film magnetic head in
accordance with an embodiment of the present invention;
[0017] FIG. 2 is a perspective view of the essential part of the
magnetoresistance effect element of the thin film magnetic head
shown in FIG. 1, showing the air bearing surface thereof;
[0018] FIG. 3 is a partially enlarged perspective view of FIG.
2;
[0019] FIG. 4 is a schematic view illustrating the magnetization of
the first and second magnetic layers;
[0020] FIG. 5 is a flowchart of inspection of the magnetic
characteristics of the thin film magnetic head in accordance with
an embodiment of the present invention;
[0021] FIG. 6 is a perspective view of a row bar having many
sliders formed therein;
[0022] FIG. 7 is a conceptual view of a row bar showing the top
surface thereof with regard to the direction of stacking, the row
bar being disposed opposite to a magnetic field applying row
bar;
[0023] FIG. 8A is a cross-sectional view taken along line 8A-8A of
FIG. 7, in which a first magnetic field applying element is
disposed opposite to the magnetic field sensor of the corresponding
thin film magnetic head;
[0024] FIG. 8B is a cross-sectional view taken along line 8B-8B of
FIG. 7, in which a second magnetic field applying element is
disposed opposite to the corresponding lapping guide;
[0025] FIGS. 9A and 9B are conceptual views illustrating a change
in the output voltage of a lapping guide when magnetic field
applying row bar B' is moved in directions "x" and "y",
respectively;
[0026] FIGS. 10A and 10B are conceptual views illustrating a change
in the output voltage of a magnetic field sensor when magnetic
field applying row bar B' is moved in directions "x" and "y",
respectively; and
[0027] FIG. 11 is a graphical view illustrating the relationship
between the intensity of a magnetic field and the output voltage of
a magnetic field sensor that is obtained by the method for
inspecting the magnetic characteristics of a thin film magnetic
head in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] First, a description will be made of a general outline of a
thin film magnetic head to which the present invention is applied.
The present invention is applicable to a thin film magnetic head
that is provided with any element that utilizes the
magnetoresistance effect. Examples of these elements include a CIP
(Current in Plane)-GMR element in which a sense current flows in
parallel with the film plane thereof, a CPP (Current Perpendicular
to the Plane)-GMR element and a TMR (Tunnel Magneto-resistance)
element in both of which a sense current flows perpendicularly to
the film plane thereof. An example of a thin film magnetic head
that is particularly suitable for the present invention will be
described. In the magnetoresistance effect element of a thin film
magnetic head, the function of a magnetic field sensor is achieved
by a pair of magnetic layers, which are stacked in the vertical
direction and whose magnetization directions change according to an
external magnetic field, and an intermediate layer that is
interposed between the pair of magnetic layers, as will be
described later.
[0029] FIG. 1 is a cross-sectional view of the essential part of a
thin film magnetic head described above. FIG. 2 is a perspective
view illustrating the essential part of the magnetoresistance
effect element of the thin film magnetic head in FIG. 1, showing
the air bearing surface thereof. FIG. 3 is a partially enlarged
perspective view of FIG. 2. The air bearing surface refers to a
surface of the thin film magnetic head that faces a recording
medium.
[0030] Thin film magnetic head 9 includes magnetoresistance effect
element (magnetic field detecting element) 1 and write head portion
2, both of which are formed on substrate 91. Magnetoresistance
effect element 1 includes magneto-resistive (MR) stack 5 having
many stacked layers, upper shield electrode layer 3 and lower
shield electrode layer 4. Upper shield electrode layer 3 and lower
shield electrode layer 4 are provided to sandwich MR stack 5 in
direction P that is perpendicular to the film plane (stacking
direction). The leading end of MR stack 5 is arranged exposed on
air bearing surface ABS. MR stack 5 is configured to allow a sense
current to flow in direction P that is perpendicular to the film
plane under a voltage that is applied between upper shield
electrode layer 3 and lower shield electrode layer 4. The magnetic
field of a recording medium, not illustrated, at a position that is
opposite to MR stack 5 changes with rotation of the recording
medium. The change in the magnetic field is detected as a change in
electrical resistance that is caused by the magnetoresistance
effect. Magnetoresistance effect element 1 uses this principle to
read magnetic information written in the recording medium. Bias
magnetic layer 6 for applying a bias magnetic field to MR stack 5
is provided on the back side of MR stack 5, as viewed from the air
bearing surface. Table 1 shows the film configuration of the
essential part of magnetoresistance effect element 1.
TABLE-US-00001 TABLE 1 Compo- Thickness Layer Configuration sition
(nm) Upper shield electrode layer 3 NiFe 5.0 Exchange coupling
transfer layer 59 Ru 0.8 Gap adjustment layer 58 CoFe 1.0 Exchange
coupling adjustment layer 57 Cu 0.9 Second magnetic layer 56 CoFe
4.0 Intermediate layer 55 ZnO 1.2(ZnO) or {close oversize brace}
Magnetic {close oversize brace} MR stack 5 MgO 0.5(MgO) field
sensor 7 First magnetic layer 54 CoFe 4.0 Exchange coupling
adjustment layer 53 Cu 0.9 Gap adjustment layer 52 CoFe 1.0
Exchange coupling transfer layer 51 Ru 0.8 Lower shield electrode
layer 4 NiFe 5.0
[0031] Referring to FIGS. 2 and 3, MR stack 5 includes a pair of
upper and lower magnetic layers (first magnetic layer 54 provided
on the lower side of the stack and second magnetic layer 56
provided on the upper side of the stack) whose magnetization
directions change according to an external magnetic field.
Intermediate layer 55, which is made of ZnO or MgO, is provided
between first and second magnetic layers 54, 56. Exchange coupling
transfer layer 51, gap adjustment layer 52, and exchange coupling
adjustment layer 53 are provided between first magnetic layer 54
and lower shield electrode layer 4. Similarly, exchange coupling
adjustment layer 57, gap adjustment layer 58, and exchange coupling
transfer layer 59 are provided between second magnetic layer 56 and
upper shield electrode layer 3. Each of exchange coupling transfer
layers 51, 59 is made of a ruthenium (Ru) layer having a thickness
of approximately 0.8 nm. Each of gap adjustment layers 52, 58 is
made of a CoFe layer having a thickness of approximately 1 nm. Each
of exchange coupling adjustment layers 53, 57 is made of a copper
(Cu) layer having a thickness of 0.9 nm.
[0032] Upper shield electrode layer 3 and lower shield electrode
layer 4 are magnetized in directions that are anti-parallel to each
other. The term "anti-parallel" means that the directions of
magnetization are parallel with each other but opposite to each
other. Various methods can be applied to fix the magnetization
directions of upper shield electrode layer 3 and lower shield
electrode layer 4 in anti-parallel directions. In the present
embodiment, upper shield electrode layer 3 and lower shield
electrode layer 4 are formed into elongated shapes that extend
along track width direction T, as illustrated in FIG. 2. Both
layers are magnetized in a single magnetic domain due to the shape
anisotropy effect, and are magnetized in directions that are
anti-parallel to each other. Alternatively, antiferromagnetic
layers may be provided adjacent to upper shield electrode layer 3
and lower shield electrode layer 4, respectively, to fix the
magnetization directions thereof by using antiferromagnetic
coupling.
[0033] First magnetic layer 54 forms a positive exchange coupling
with upper shield electrode layer 3 via first exchange coupling
transfer layer 51, first gap adjustment layer 52, and first
exchange coupling adjustment layer 53. As a result, first magnetic
layer 54 is subjected to a force that magnetizes first magnetic
layer 54 in the same direction as lower shield electrode layer 4,
as shown by the arrows in FIGS. 2 and 3. Similarly, second magnetic
layer 56 forms a positive exchange coupling with upper shield
electrode layer 3 via second exchange coupling transfer layer 59,
second gap adjustment layer 58, and second exchange coupling
adjustment layer 57. As a result, second magnetic layer 56 is
subjected to a force that magnetizes second magnetic layer 56 in
the same direction as upper shield electrode layer 3, as shown by
the arrows in FIGS. 2 and 3.
[0034] FIG. 4 is a schematic view illustrating the magnetization of
the first and second magnetic layers. As described above, bias
magnetic layer 6 is provided on the back side of MR stack 5, as
viewed from air bearing surface ABS. Bias magnetic layer 6 is
magnetized in the direction that is perpendicular to air bearing
surface ABS, as shown by the solid black arrow in the figure. As a
result, first and second magnetic layers 54, 56 are subjected to a
magnetic field that is perpendicular to air bearing surface ABS.
Thus, first and second magnetic layers 54, 56 not only form an
exchange coupling with upper shield electrode layer 3 and lower
shield electrode layer 4, respectively, but also receive a bias
magnetic field from bias magnetic layer 6. As a result, the
magnetization directions of first and second magnetic layers 54,
56, which are represented by the arrows in dotted lines, are
rotated in opposite directions by predetermined angle .theta., as
shown by the arrows in solid lines in FIG. 4, and ideally form
right angles.
[0035] If an external magnetic field is applied under this state,
as shown by the white bold arrows in the figure, then the
magnetization directions of first and second magnetic layers 54, 56
are rotated in opposite directions depending on the direction of
the external magnetic field. Specifically, the external magnetic
field that is applied in direction A in the figure will rotate the
magnetization directions of first and second magnetic layers 54, 56
in direction "a" in the figure. The external magnetic field that is
applied in direction B in the figure will rotate the magnetization
directions of first and second magnetic layers 54, 56 in direction
"b" in the figure. This causes a change in the angle formed between
the magnetization directions of first and second magnetic layers
54, 56 depending on the external magnetic field, and thereby causes
a change in the resistance of a sense current based on the
magnetoresistance effect. The direction and intensity of the
external magnetic field can thus be detected by magnetoresistance
effect element 1.
[0036] In this way, the pair of magnetic layers 54, 56 whose
magnetization directions change according to an external magnetic
field and intermediate layer 55 that is interposed therebetween
function as magnetic field sensor 7 in magnetoresistance effect
element 1 of the present embodiment. Magnetoresistance effect
element 1 having intermediate layer 55 that is made of a metal or
made of a semiconductor, such as ZnO, functions as a CPP-GMR
element, whereas magnetoresistance effect element 1 having
intermediate layer 55 that is made of an insulator, such as MgO,
functions as a TMR element.
[0037] Referring again to FIG. 1, write head portion 2 is provided
above magnetic field detecting element 1 via inter-element shield
layer 8 that is formed by means of sputtering or the like. Write
head portion 2 has an arrangement for so-called perpendicular
magnetic recording. Magnetic pole layers for writing have main
magnetic pole layer 21 and auxiliary magnetic pole layer 22. These
magnetic pole layers 21, 22 are formed by frame plating or the
like. Main magnetic pole layer 21, which is made of FeCo, is
exposed on air bearing surface ABS substantially perpendicularly
thereto. Coil layer 23, which extends above gap layer 24 made of an
insulating material, is wound around main magnetic pole layer 21 in
order to induce a magnetic flux within main magnetic pole layer 21.
Coil layer 23 is formed by means of frame plating or the like. The
magnetic flux is guided inside main magnetic pole layer 21 and is
emitted from air bearing surface ABS toward the recording medium.
Main magnetic pole layer 21 is reduced in dimension not only in
direction P that is perpendicular to the film plane but also in
track width direction T (i.e., the direction that is perpendicular
to the drawing of FIG. 1) in the vicinity of air bearing surface
ABS, thereby producing a concentrated and intense writing magnetic
field that realizes high recording density.
[0038] Auxiliary magnetic pole layer 22 is a magnetic layer that is
magnetically coupled to main magnetic pole layer 21. Auxiliary
magnetic pole layer 22 is a magnetic pole layer which has a
thickness of about 0.01 to about 0.5 .mu.m and which is made of an
alloy that consists of at least two of Ni, Fe and Co. Auxiliary
magnetic pole layer 22 is branched from main magnetic pole layer 21
and is provided opposite to main magnetic pole layer 21 via gap
layer 24 and coil insulating layer 25 at air bearing surface ABS.
Auxiliary magnetic pole layer 22 has a trailing shield portion
having a wider layer section than the rest of auxiliary magnetic
pole layer 22 at the end portion that is on the side of air bearing
surface ABS. Auxiliary magnetic pole layer 22 having such an
arrangement provides a steeper magnetic field gradient between
auxiliary magnetic pole layer 22 and main magnetic pole layer 21 in
the vicinity of air bearing surface ABS. As a result, it is
possible to reduce signal output jitter, thereby to lower the error
rate in reading.
[0039] Insulating layers 92, 93 are formed in the portion in which
magnetoresistance effect element 1 and write head portion 2
described above are not provided.
[0040] Next, an explanation will be made of a method for inspecting
the magnetic characteristics of the above-described thin film
magnetic heads arranged in a row bar, with reference to the
flowchart of FIG. 5. It should be noted that the inspecting method
described hereinafter is carried out as part of the manufacturing
process of the thin film magnetic head.
[0041] (Step S1) First, row bar B having a plurality of sliders S
is prepared. Sliders S, each having thin film magnetic head 9
formed therein, are arranged along longitudinal direction "x" of
row bar B. Row bar B is fabricated by dicing a wafer to separate a
part of many sliders formed on the wafer. FIG. 6 is a perspective
view of a row bar having many sliders formed therein. FIG. 7 is a
conceptual view of a row bar showing the top surface thereof with
regard to the direction of stacking, the row bar being disposed
opposite to a magnetic field applying row bar, which will be
described later. It should be noted that only pads are actually
provided on the top surface of the row bar in the figure. The other
elements and coils are actually provided inside the row bar,
although they are depicted on the top surface of the row bar for
illustrative purpose. Each slider S has magnetoresistance effect
element 1 of thin film magnetic head 9 formed therein.
Magnetoresistance effect element 1 is formed such that it will
appear on the cutting plane when a wafer is diced. By lapping the
cutting plane, which is lapping surface LS, magnetoresistance
effect element 1 having a predetermined element height MRH is
formed (see FIG. 1). For simplicity of illustration, only twelve
sliders S are provided in row bar B. However, sliders S may be
provided in any numbers, and 50 to 100 sliders may often be
provided in an actual bar. Referring to FIG. 7, pads 11a, 11b and
pads 12a, 12b are provided on the top surface of slider S with
regard to the stacking direction. Pads 11a, 11b are connected to
magnetoresistance effect element 1 and apply a sense current
thereto. Pads 12a, 12b are connected to write head portion 2 and
apply a current to coil 24. Adjacent to pads 12a, 12b, pads 12c,
12d are provided for a heater coil that locally heats the inside of
slider S. By providing heat via pads 12c, 12d, magnetoresistance
effect element (magnetic field detecting element) 1 and write head
portion 2 protrude by approximately several nanometers on air
bearing surface ABS, causing a reduction in the magnetic space
between magnetoresistance effect element (magnetic field detecting
element) 1 and a recording medium, as well as between write head
portion 2 and a recording medium.
[0042] Inter-element gaps G are provided between sliders S that are
aligned in a line. Inter-element gaps G also serve as dicing
margins when row bar B is separated into sliders S. In
inter-element gap G, lapping guide L is provided on lapping surface
LS. In the illustrated row bar B, lapping guides L are provided
between each pair of adjacent sliders S in row bar B and at both
ends of row bar B. However, lapping guides L may be provided at
least two locations selected from locations between adjacent
sliders S and locations at ends of row bar B.
[0043] Lapping guide L, which is generally referred to as an RLG
(Resistance Lapping Guide) element or as an ELG (Electric Lapping
Guide) element, has the film configuration of a CIP element in
which a sense current flows in parallel with the film plane.
Lapping guide L may have the same film configuration as MR stack 5,
but is adapted to be supplied with a sense current, not from upper
and lower shield layers, but from a pair of lead electrode films
15a, 15b that are provided on both sides of MR stack 5 with regard
to the track width direction thereof. Lapping guide L exhibits a
magnetoresistance effect, and is fabricated almost simultaneously
with MR stack 5 in the wafer process. Both ends 14a, 14b of lapping
guide L are electrically connected to pads 13a, 13b that are
provided on the top surface of inter-element gap G with regard to
the stacking direction, and a voltage between both ends 14a, 14b of
lapping guide L can be detected by means of probes that are placed
on pads 13a, 13b. In a lapping step performed prior to this step,
lapping surface LS is lapped while a current is applied to lapping
guide L. Lapping guide L is lapped together with MR stack 5, and
consequently, element height LH (see FIG. 7) of lapping guide L
decreases and the electrical resistance thereof increases. MR stack
5 having predetermined element height MRH (see FIG. 7) can be
fabricated by using a relationship between the electrical
resistance of lapping guide L and the lapping amount of lapping
guide L that is obtained in advance. Lapping guide L does not
require a significantly small element size because the fundamental
function thereof is to detect a change in electrical resistance at
the time of lapping. Lapping guide L typically has a width of
several micrometers in the longitudinal direction "x" thereof.
[0044] (Step S2) Next, magnetic field applying row bar B' is
prepared. Magnetic field applying row bar B' is provided with first
magnetic field applying elements 71 that correspond to thin film
magnetic heads 9, respectively, and at least two second magnetic
field applying elements 72 that correspond to lapping guides L. As
will be described later, the locations of first magnetic field
applying elements 71 and second magnetic field applying elements 72
are set such that first magnetic field applying elements 71 face
magnetic field sensors 7 of thin film magnetic head 9,
respectively, and second magnetic field applying elements 72 face
lapping guides L, respectively, when magnetic field applying row
bar B' is disposed opposite to row bar B. First magnetic field
applying elements 71 are provided in as many numbers as sliders S.
Magnetic field applying row bar B' is fabricated in the wafer
process, as with row bar B, and this enables highly precise
positioning of first magnetic field applying elements 71 and second
magnetic field applying elements 72. Further, magnetic field
applying row bar B' has a surface that is lapped in the same way as
row bar B and that is arranged opposite to row bar B.
[0045] Second magnetic field applying elements 72 do not have to be
provided opposite to all lapping guides L. However, magnetic field
applying row bar B' requires precise positioning relative to row
bar B in the longitudinal direction "x" thereof, as well as in
direction "y" that is perpendicular to the longitudinal direction
"x". For this reason, the relative positional relationship between
row bar B and magnetic field applying row bar B' should be
monitored at least two locations. To this end, second magnetic
field applying elements 72 are preferably provided at least both
ends of magnetic field applying row bar B' so that they face
lapping guides L at both ends of row bar B. However, second
magnetic field applying elements 72 may be provided such that they
face lapping guides L at locations between sliders S, as long as
the aforementioned objective can be achieved. Furthermore, three or
more second magnetic field applying elements 72 may be provided in
order to enhance accuracy in positioning. For example, second
magnetic field applying elements 72 may be provided at four
locations in total (shown as P1 to P4 in FIG. 6), i.e., two
intermediate locations obtained by trisecting magnetic field
applying row bar B' in the longitudinal direction "x", in addition
to both ends of magnetic field applying row bar B'.
[0046] First magnetic field applying element 71 has the same
structure as write head portion 2 of thin film magnetic head 9.
Consequently, the magnetic pole layer has main magnetic pole layer
21' and auxiliary magnetic pole layer 22', and main magnetic pole
layer 21' is exposed on air bearing surface ABS substantially
perpendicularly thereto, although detailed explanation is omitted.
Coil layer 23', which extends above gap layer 24' made of an
insulating material, is wound around main magnetic pole layer 21'
in order to induce a magnetic flux within main magnetic pole layer
21'. In order to concentrate a magnetic field onto magnetic field
sensor 7 having a significantly small width, such as several tens
of nanometers, in the track width direction thereof, first magnetic
field applying element 71, similar to write head portion 2 of thin
film magnetic head 9, has a limited width of several tens of
nanometers in the track width direction, i.e., in the direction
"x". In addition, in order to apply an intensive magnetic field
onto magnetic field sensor 7 with regard to direction P that is
perpendicular to the film plane, first magnetic field applying
element 71 preferably has almost the same width in direction P as
magnetic field sensor 7. This prevents a large magnetic field from
being applied to upper and lower shield layers 3, 4. First magnetic
field applying element 71 can apply an alternating magnetic field
to magnetic field sensor 7 of thin film magnetic head 9 opposite
thereto while varying the intensity of the magnetic field. The
frequency of the alternating magnetic field can be determined as
appropriate, according to the actual environment in a hard disk
drive.
[0047] Second magnetic field applying element 72 applies a magnetic
field to lapping guide L that is opposite thereto. Second magnetic
field applying element 72 has the same structure as write head
portion 2 of thin film magnetic head 9. Consequently, the magnetic
pole layer has main magnetic pole layer 21'' and auxiliary magnetic
pole layer 22'', and main magnetic pole layer 21'' is exposed on
air bearing surface ABS substantially perpendicularly thereto,
although detailed explanation is omitted. Coil layer 23'', which
extends above gap layer 24'' made of an insulating material, is
wound around main magnetic pole layer 21'' in order to induce a
magnetic flux within main magnetic pole layer 21''. In order to
effectively apply a magnetic field to lapping guide L having a
width of several micrometers in the longitudinal direction "x", the
width in the longitudinal direction "x" is preferably several
micrometers, similar to lapping guide L.
[0048] In the present embodiment, first and second magnetic field
applying elements 71, 72 are provided with write magnetic pole
layers for the so-called perpendicular magnetic recording type.
However, needless to say, the elements may alternatively have a
magnetic pole structure for the horizontal magnetic recording
type.
[0049] (Step S3) Next, magnetic field applying row bar B' is
disposed opposite to row bar B such that magnetic pole end 73 of
first magnetic field applying element 71 is opposite to magnetic
field sensor 7 of corresponding thin film magnetic head 9 and such
that magnetic pole end 74 of second magnetic field applying element
72 is opposite to corresponding lapping guide L (first positioning
step). FIG. 8A is a cross-sectional view taken along line 8A-8A of
FIG. 7, in which first magnetic field applying element 71 is
disposed opposite to magnetic field sensor 7 of corresponding thin
film magnetic head 9. FIG. 8B is a cross-sectional view taken along
line 8B-8B of FIG. 7, in which second magnetic field applying
element 72 is disposed opposite to corresponding lapping guide L.
Magnetic field applying row bar B' is spaced apart from row bar B
in these figures, but may be in contact with row bar B. Further,
there may be a small gap between magnetic field applying row bar B'
and row bar B, as illustrated in these figures, in order to protect
the air bearing surface of row bar B.
[0050] In the following positioning steps S3, S4 and S5, the
relative movement between magnetic field applying row bar B' and
row bar B is adapted to occur as a rectilinear movement in the
longitudinal direction "x", as a rectilinear movement in the
direction "y" that is perpendicular to the film plane and as a
rotational movement about direction "z" (z-axis), wherein the
direction "z" is defined to be a direction that is both
perpendicular to the longitudinal direction "x" of row bar B and
perpendicular to the direction "y". Means for realizing such
movements can be selected as needed. The means includes, for
example, attaching row bar B to an appropriate fixing means and
attaching magnetic field applying row bar B' to an x-y stage that
is capable of moving according to the three degrees of freedom
described above. The rotational movement about the direction "z"
corrects the possible state in which row bar B and magnetic field
applying row bar B' are mounted askew relative to each other.
However, if sufficient accuracy in mounting is ensured and
adjustment of rotational angles in the direction "z" is not
necessary, then the adjustment can be made only by rectilinear
movements in the directions "x" and "y".
[0051] The positioning in this step is made in order to roughly
position magnetic field applying row bar B' relative to row bar B.
Methods for the positioning include, for example, making the edges
of row bar B' and the edges of row bar B correspond with each other
by using mechanical or optical monitoring means. The accuracy in
positioning is, so to speak, a mechanically achievable level, and
may be insufficient. However, this step provides rough but simple
positioning means and enables the second and third positioning
steps, which will be described later, to be performed in a more
efficient manner.
[0052] (Step S4) Next, after first positioning step S3, a magnetic
field is applied to lapping guides L from second magnetic field
applying elements 72 while an electrical current is applied to
lapping guides L. Further, a relative movement between magnetic
field applying row bar B' and row bar B is made so that at least
one lapping guide L exhibits the largest output voltage (the second
positioning step). By applying a magnetic field to lapping guide L,
which has magnetic layers that exhibit the magnetoresistance effect
as described above, a variation in the electrical resistance of a
sense current occurs according to the intensity of the magnetic
field, and thereby, a variation in the voltage between both ends
14a, 14b of lapping guide L is caused. FIG. 9A is a conceptual view
illustrating a change in the output voltage of lapping guide L when
magnetic field applying row bar B' is moved in the direction "x".
When magnetic field applying row bar B' is moved in the direction
"x" and second magnetic field applying element 72 comes to a
position that is substantially opposite to lapping guide L with
regards to the direction "x", lapping guide L is subjected to the
largest magnetic field and thereby exhibits the largest output
voltage. Similarly, FIG. 9B is a conceptual view illustrating a
change in the output voltage of lapping guide L when magnetic field
applying row bar B' is moved in the direction "y". When magnetic
field applying row bar B' is moved in the direction "y" and second
magnetic field applying element 72 comes to a position that is
substantially opposite to lapping guide L with regards to the
direction "y", lapping guide L is subjected to the largest magnetic
field and thereby exhibits the largest output voltage. The
adjustment in the direction "x" may precede the adjustment in the
direction "y", and vice versa. When the adjustments for both
directions are made so that lapping guide L exhibits the largest
output voltage, second magnetic field applying element 72 comes to
a position that is substantially opposite to lapping guide L.
[0053] On completion of these processes, second magnetic field
applying element 72 comes to a position that is substantially
opposite to lapping guide L in a region in which lapping guide L
has been subjected to the positioning adjustment. However, there is
actually the possibility in which magnetic field applying row bar
B' and row bar B are disposed askew relative to each other. Hence,
after a positioning adjustment is completed based on one lapping
guide L, another positioning adjustment is preferably performed
based on another lapping guide L. By rotating magnetic field
applying row bar B' about the position of lapping guide L that has
already been adjusted, the orientation (the rotational angle) of
magnetic field applying row bar B' can be adjusted so that magnetic
field applying row bar B' and row bar B become parallel with each
other. Needless to say, it is also possible to perform positioning
adjustment based on the linear movements in the directions "x" and
"y", as well as the rotational movement about the z-axis, while
simultaneously monitoring the output voltages of more than one
lapping guide L.
[0054] This step makes it possible to perform the positioning of
magnetic field applying row bar B' and row bar B with more accuracy
than in first positioning step S3. It should be noted that the
accuracy obtained in this step depends on the width and the
magnetoresistance ratio of lapping guide L. However, if the
positioning adjustment is performed with sufficient accuracy in
this step, then it is possible to omit third positioning step S5
that follows and to go to measurement step S6.
[0055] (Step S5) Next, a magnetic field is applied from first
magnetic field applying element 71 to magnetic field sensor 7 of
thin film magnetic head 9 while an electric current is applied to
magnetic field sensor 7. Then, a relative movement between magnetic
field applying row bar B' and row bar B is made so that magnetic
field sensor 7 exhibits the largest output voltage (third
positioning step). The process in this step is similar to second
positioning step S4, but differs from step S4 in that the output
voltage of magnetic field sensor 7 is used in place of the output
voltage of lapping guide L. Specifically, when magnetic field
applying row bar B' is moved in the direction "x" and first
magnetic field applying element 71 comes to a position that is
substantially opposite to the magnetic field sensor with regards to
the direction "x", magnetic field sensor 7 is subjected to the
largest magnetic field and also exhibits the largest output
voltage. Further, when magnetic field applying row bar B' is moved
in the direction "y" and first magnetic field applying element 71
comes to a position that is substantially opposite to the magnetic
field sensor with regards to the direction "y", magnetic field
sensor 7 is subjected to the largest magnetic field and also
exhibits the largest output voltage. The adjustment in the
direction "x" may precede the adjustment in the direction "y", and
vice versa. When the adjustments for both directions are completed
so that magnetic field sensor 7 exhibits the largest output
voltage, first magnetic field applying element 71 comes to a
position that is substantially opposite to magnetic field sensor
7.
[0056] FIG. 10A is a conceptual view illustrating a change in the
output voltage of magnetic field sensor 7 when magnetic field
applying row bar B' is moved in the direction "x". Similarly, FIG.
10B is a conceptual view illustrating a change in the output
voltage of magnetic field sensor 7 when magnetic field applying row
bar B' is moved in the direction "y". As will be apparent from the
comparison between these figures and FIGS. 9A and 9B, the output
relative to the movement in the direction "x" or "y" exhibits a
more sensitive change. This is because magnetic field sensor 7 has
a significantly smaller width in the track width direction than
lapping guide L. As described above, magnetic field sensor 7 has a
track width direction in the order of several tens of nanometers,
whereas lapping guide L has a track width direction in the order of
several micrometers. Thus, there is a difference in the width by a
factor of hundreds. Consequently, step S5 makes it possible to
adjust first magnetic field applying element 71 to a position that
is almost completely opposite to magnetic field sensor 7.
[0057] It should be noted that all of first magnetic field applying
elements 71 do not have to be monitored, although magnetic field
applying elements 71 are provided in as many numbers as sliders S
so that each magnetic field applying element 71 corresponds to each
magnetic field sensor 7. The adjustment can be suitably performed
only by using first magnetic field applying elements 71 near both
ends of magnetic field applying row bar B' and magnetic field
sensors 7 near both ends of row bar B. Magnetic field sensor 7 in
each slider S is formed in sufficiently accurate dimensions and in
a sufficiently accurate array pitch in the wafer process. First
magnetic field applying element 71 in magnetic field applying row
bar B' is also formed in sufficiently accurate dimensions and in a
sufficiently accurate array pitch in the wafer process.
Accordingly, as a result of using first magnetic field applying
elements 71 near both ends of magnetic field applying row bar B' in
order to adjust the position of magnetic field applying row bar B',
the other first magnetic field applying elements 71 are
automatically placed in positions that are opposite to respective
magnetic field sensors 7.
[0058] (Step S6) After the third positioning step, an alternating
magnetic field is applied, from first magnetic field applying
elements 71 to magnetic field sensors 7 of thin film magnetic heads
9, while an electric current is applied to magnetic field sensors
7, and while the intensity of the magnetic field is changed, and
therefore the relationship between the intensity of the magnetic
field and the output voltage of the magnetic field sensor is
obtained (measurement step). The output voltage obtained by
magnetic field sensors 7 is measured by pads 11a, 11b on slider S
through probes or the like. As a result, a measurement result, such
as the one shown in FIG. 11, is obtained for each slider S. The
figure shows an example of the output voltage when an alternating
magnetic field having a frequency of 1 megahertz is applied. The
line shown by symbol F in the figure denotes the output versus a
magnetic field with increasing intensity, while the line shown by
symbol R denotes the output versus a magnetic field with decreasing
intensity. The step is basically the same as in the conventional
QST. However, this step differs from the conventional QST in that a
plurality of first magnetic field applying elements 71 is provided
such that each first magnetic field applying element corresponds to
each slider S and in that individual first magnetic field applying
element 71 applies a magnetic field to corresponding magnetic field
sensor 7.
[0059] According to the present embodiment, first magnetic field
applying element 71 has substantially the same structure as a
conventional write element and is capable of generating an
alternating magnetic field of several megahertz without difficulty.
This makes it possible to create a test environment that well
simulates the actual condition in a hard disk drive as regards
generation of a magnetic field, and thereby improves reliability of
the test.
[0060] In addition, when the present embodiment is applied to the
above-described thin film magnetic head, the following specific
effects can be expected. Specifically, the above-described thin
film magnetic head has upper and lower shield electrode layers
which are magnetized in directions that are anti-parallel to each
other and has a pair of magnetic layers which are exchange-coupled
with the shield electrode layers. While this state is maintained,
the pair of magnetic layers is magnetized by a bias magnetic field
so that the magnetization directions thereof are perpendicular to
each other, and the pair of magnetic layers is further magnetized
so that the angle between the magnetization directions of the pair
of magnetic layers is changed by the effect of an external magnetic
field. In such a thin film magnetic head, the upper and lower
shield electrode layers not only serve as magnetic shields but also
directly affect the magnetization state of the pair of magnetic
layers, and accordingly, the state of the shield electrode layers
in which the magnetization directions are anti-parallel with each
other should be maintained even during a test. The intensity of a
magnetic field applied in the QST is significantly larger than that
in the actual environment within a hard disk drive. Thus, the
magnetization of the upper and lower shield electrode layers may be
disturbed by a magnetic field that is applied during the test, and
the characteristics of a magnetoresistance effect element may be
greatly affected. This may make an appropriate test impossible. In
the present embodiment, the first magnetic field applying element
locally exerts a magnetic field on a corresponding magnetic field
sensor, and the upper and lower shield electrode layers are
subjected to a magnetic field that is significantly smaller than
that applied in the QST. Consequently, the above-described problems
can be easily solved.
[0061] The method for inspecting the magnetic characteristics using
a magnetic field applying bar has such advantages as described
above. However, it is necessary for each first magnetic field
applying element to be precisely arranged opposite to the
corresponding magnetic field sensor. It should be noted that this
is a problem that is specific to the method for inspecting magnetic
characteristics using a magnetic field applying bar and that this
is also a problem that occurs only if the method for inspecting
magnetic characteristics using a magnetic field applying bar, which
is novel per se, has been invented. However, this problem can also
be solved effectively by magnetic positioning that uses a lapping
guide as a positioning sensor and, if necessary, by magnetic
positioning that uses a magnetic field sensor as a positioning
sensor. The lapping guide is commonly introduced in the
manufacturing process of conventional thin film magnetic heads in
order to monitor the lapping amount of the elements. Generally
speaking, this does not mean that any additional elements are
required in the wafer process. It should be noted that the present
embodiment can be basically carried out simply by replacing a
conventional Helmholtz coil with a magnetic field applying bar.
[0062] Although certain preferred embodiments of the present
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
without departing from the spirit or scope of the appended
claims.
* * * * *